The SEDRIS Data Representation Model
APPENDIX A - Classes
Spatial Index Related Geometry Topology

Class Name: Spatial Index Related Geometry Topology

Superclass - <Geometry Topology Hierarchy>

Subclasses

This DRM class is concrete and has no subclasses.

Definition

An instance of this DRM class encodes a spatially indexed (tiled) organization of primitive <Geometry Topology> objects.

Primary Page in DRM Diagram:

Secondary Pages in DRM Diagram:

This class appears on only one page of the DRM class diagram.

Example

No Example supplied.

FAQs

Why an aggregate object instead of a hierarchy or some other type of SEDRIS object?

We need a 'branch', and each branch from an aggregation is a hierarchy object, because <Aggregate Geometry> instances contain <Geometry Hierarchy> instances. When an <Aggregate Geometry> instance has a <Geometry Topology Hierarchy>, that <Aggregate Geometry> represents a distinct topological surface. We shall organize a topological surface, a.k.a. an "independent topology", which eventually, in SEDRIS, is 'rooted at' a single <Aggregate Geometry> instance.

The <Geometry Hierarchy> instances are either <Aggregate Geometry>, or <Property Grid Hook Point>, or or <Geometry Model Instances>. The topological organization of a <Model>, if any, is contained within the <Model>, so we're left with a need to specify the topological organization of an <Aggregate Geometry> instance. The organizing principle shall be applied at the <Aggregate Geometry> level - no lower, no higher.

The same spatial indexing structure can be shared by multiple <Aggregate Geometry> because there could exist multiple classification organizations of the same set of <Geometry>. When a single set of <Geometry> is organized by multiple classification approaches, it's still the same set of <Geometry> being dealt with, and still the same set of <Geometry Node>, <Geometry Edge>, and <Face> instances. Changing the logical organization of the <Geometry> has no effect on the spatial organization of the underlying topological primitives. Thus, one spatial organization for a set of topological primitives may be shared by many different organizations (aggregations) of <Geometry> where the <Geometry> are composed of the same spatially organized topological primitives, regardless of which organization the <Geometry> are viewed from.

Constraints

Composed of (two-way)

Component of (two-way)(inherited)

Inherited Field Elements

SE_Geometry_Topology_Level geometry_topology_level;

Field Elements

SE_Boolean sparse; (notes)
SE_Integer_Positive column_count;
SE_Integer_Positive row_count;
SE_Long_Float column_width; (notes)
SE_Long_Float row_width; (notes)
SE_Spatial_Index_Spacing_Unit spacing_unit;

Notes

Composed of Notes


Location

 This is the origin of the collection, which is the lower-left corner.

Fields Notes


sparse

 If this value is SE_FALSE, all column and row entries are present;
 otherwise one or more entries are not present.

column_width

 This is the length of a cell in the given unit along the X axis.

row_width

 This is the length of a cell in the given unit along the Y axis.
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Last updated: May 15, 2003 Copyright © 2003 SEDRIS™